High precision MT connector inspection machine
￼This system uses image processing techniques and a laser heterodyne to measure multi-core optical connectors, the waveguide pitch deviation and shape with a high precision. It also takes the measurements at an optimal magnification using a special optical system.
|Repeat measurement precision||3σ≦0.1μm|
|Measurement time||1 – 2 sec/1 core, 1 groove|
- Measure between guide holes.
- Measure the pitch and deviation against the design value in the X-axis (left and right directions) between the ferrule holes from the center line between the guide hole positions.
- Measure the deviation in the Y-axis (up and down directions) of the ferrule hole using the guide hole position as the center line.
- Measure the internal diameter of the guide hole and ferrule hole.
|Microscope||Infinite optical system subject lens
|CCD||2456 × 2058 (pixels)|
|Light source system 1 (co-axial reflection light)||LED light external control|
|Light source system 1 (co-axial reflection light)||LED light external control|
|Auto X,Y,Z stage||
|Laser interference (2-axis)||
|Tape fiber incident unit||Custom-made|
|Auto stage controller||X, Y, Z-axis stage control|
- Vibration isolation table (auto-levelling system, continuous air supply system)
- Calibration glass pattern gauge
This product is a system to take dimensional measurements at a high accuracy by improving the reproducibility of images taken with a special optical system and high resolution camera using a unique image processing algorithm, by mounting a laser interference meter to measure the movement to raise the reliability of the values, and by controlling the XYZ auto stage and light intensity using a PC, with standard values being set for the inspection.
The measurement subjects of this system are the MT ferrules, MTF fiber assemblies and MPOs of optical communication parts. These optical communication parts are manufactured with a high degree of precision in order to keep the connection loss at a minimum and maintain a high density with the same shape. As one of the few systems available in the world to take such stringent measurements, the systems that we have delivered are rated highly by manufacturers of optical communication parts both in Japan and overseas.
An explanation of the system outline and measurement details for each measurement subject is given below.
Description of measurement details
For the dimensional measurement of a MT connector, the system measures the distance between the guide holes, the distance in the horizontal direction of the ferrule hole from the center reference between the guide holes, the distance in the vertical direction of the ferrule hole from the virtual reference between the guide holes, the distance of the ferrule hole from the center reference between the guide holes, and the diameter of the guide holes and ferrule holes.
The distance between the guide holes is determined by deriving approximate circles from the end face information of the guide holes and then determining the distance between the 2 points at the centers of the approximate circles.
The distance of the ferrule hole in the horizontal direction from the center reference of the guide holes is determined by finding out the position of the ferrule hole in the horizontal direction based on the center of the distance between the 2 approximate holes derived from the guide holes and the displaced distance from the design value. The distance of the ferrule hole in the vertical direction from the virtual reference between the guide holes is determined by finding out the position of the ferrule hole in the vertical direction based on a line connecting the centers of the 2 approximate holes derived from the guide holes and the displaced distance from the design value. The distance of the ferrule hole from the center reference between the guide holes is derived from the horizontal direction (X position information) and vertical direction (Y position information) mentioned above.
The diameter of the guide hole and ferrule hole is used to derive the approximate circle based on the end face information obtained from the transmission light and represents the diameter of the circle.
Dimensional measurements of MPO connectors (part before fitting the guide pin and housing) are taken in the same way as for MT connectors.
Description of system
This product is broadly composed of the main unit and the control unit. The main unit is composed of the stand, measurement unit, XYZ auto stage/work mounting unit and observation light unit while the control unit is made up of the PC, PC rack, driver box and laser interference meter, with the system constructed on a host PC.
An outline of the main unit is explained in sequence below. The stand maintains a stable posture with the damping and auto leveling functions of the continuous air supply system, and the unit is operated with the measurement unit placed on the mounting surface.
The measurement unit uses a stone surface plate as the base to support stable measurements by enhancing the rigidity and attenuating the vibration.The XYZ auto stage, resolution 0.01 μm laser interference meter, microscope and transmission light unit are mounted on the base, and infiltration from the top during auto operation is prevented by using a cover to cover the measurement unit.
The movement of each axis on the XYZ auto stage is X-axis 100 mm, Y-axis 4 mm, Z-axis 4 mm for the standard specifications.The movement can also be customized.The drive unit uses a motor attached with an encoder to raise the correlation between the drive and movement. Each stage has an independent structure and is loaded in the ZYX sequence. 2 mirrors used for the laser interference meter are installed in the top-most X-axis to detect the movement, up and down displacement during movement, and Z-axis movement.In addition, a work holder is mounted on top of the X-axis to securely fasten the measurement subject and special parts customized for each customer so as to improve the measurement accuracy.
As the observation light unit takes the core images to be subject to the image processing, the microscope, lighting devices and CCD camera used all come from leading Japanese manufacturers in order to ensure high quality and reliability.The image sensor of the CCD camera reduces the noise in the CCD sensor and the sensor individual loss while the pixel count raises the reproducibility of the image process by employing a high resolution QSXGA CCD to capture the image vividly.LEDs are employed as the light source for the lighting devices to obtain a stable output. Besides being easier to start up on a daily basis, compared to lighting devices using electric bulbs, the maintenance cost (replacement of worn-out fan) and running cost (life and consumption power of light bulbs) are also lower.In addition, transmission lights are selected strictly for each measurement subject to significantly reduce the unevenness in the luminance on the screen.
The PC serves as a host for the control unit to control all the image processing, drive, auto focus, laser interference meter and light intensity using a variety of boards required in the original software and control.OS is Windows 7 (Japanese or English).
Multi-value processing is carried to detect a subject using a unique algorithm in the image processing. When likened to the processing data volume, if the guide holes of the MT connector are the detection subjects, the approximate circles are derived from the data volume of more than 20,000 pixels from 4 or more columns for the detection of the subject at an ambient pixel count of 5,000 pixels, and subject detection is carried out at a high speed for a processing time below the decimal point.
In order to improve the reliability of the values derived through image processing, besides reproducibility, calibration is also essential.As the XY distance on the image is also included in the derivation process in the system, the necessity for this is seriously considered by producing a specially-ordered reference pattern and performing calibration in the respective XY directions using the pattern for each measurement subject at each magnification (field of vision).The reference pattern defines the traceability system drawing and the list of inspection results.
Auto focus is one of the functions in the original software which is used to align the point to the respective focus point with good reproducibility using the reflected light and transmitted light in the focus scanning and contrast detection system.Light intensity control is also one of the functions of the original software which is used for level adjustment and turning the lights on and off. If the detected luminance is higher or lower than the luminance set, the auto light function uses the light source as a loop control to adjust the luminance to the level set.